Varistor

A varistor is an electronic component with an electrical resistance that varies with the applied voltage. A varistor is a 2 terminal semiconductor device that protects the electrical and electronic devices from overvoltage transients. Its resistance is dependent on the applied input voltage. The word varistor is formed by combining variable and resistor. It is also known as a voltage-dependent resistor, VDR whose resistance changes automatically with the corresponding change in the voltage across it. It is always placed in a shunt with the device being protected. This is basically done to protect the circuit from voltage surges.

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